Is the Loss of Perennial Arctic Sea Ice Reversible?

Recent observational evidence and climate model projections suggest that a seasonally ice free Arctic Ocean could be reached within this century. Given this and the continued increases in greenhouse gas emissions, the loss of perennial sea ice may well be unavoidable. Some have hypothesized that this may represent a "tipping point" in the climate system; with the change resulting from threshold behavior and being potentially irreversible. Here we analyze a series of climate model integrations to explore the irreversibility of perennial arctic sea ice loss. These integrations are initialized with seasonally ice free conditions obtained from a future scenario run at the end of the 21st century. The integrations apply reductions in atmospheric CO₂ concentrations that decrease at varying rates from late 21st century A1B scenario values. The forcing, timescales and dynamics that modify sea ice conditions in these integrations are analyzed and how these factors influence the possible re-establishment of the perennial arctic ice cover is discussed.